1. Field of the Invention:
The present invention relates generally to conveyors and conveying devices and more specifically, to a device which uses an arrangement of rollers to invert a conveyor belt running in an endless belt conveying system.
2. Description of the Related Art:
In an endless belt conveying system, a conveyor belt conveys material in one direction between points. At one point, articles or materials conveyed on the upper surface of the conveyor belt are discharged, and at the other point articles or material are placed on the conveyor for transport. After the material is discharged at the one point, the belt turns 180.degree. at for example, an end roller, so that the upper surface is now facing downwardly until it travels to the other point, where another end roller turns the belt 180.degree. so that the carrying surface is once again on the upper side. In some areas of use, such as in the mining arts, the distance between the two points may be measured in the thousands of feet. Thus, for the entire length of the distance between the two points, the material-carrying surface is upside down on the return run of the belting.
When the carrying side of the endless conveyor belt is in contact with a material which has a sticky nature, not all of the material will be discharged at the discharge point and thus, as the belt is inverted, a residue of material is carried upside down as the belt travels back to the pick-up point. This contamination of the conveyor belt surface can present an environmental problem, particularly where the conveyor system will cross bodies of water or other environmentally sensitive areas. The material adhering to the surface of this downward-facing return run of the endless belt conveyor falls off the belt over the length of the conveying system. Such material in time builds up and requires removal with resultant cost implications, and may in any case be undesirable if it is being dropped onto a surface which is required to be kept clean at all times.
Belt turnover devices have been used in the past to achieve an inversion of the return run of the conveyor belt so as to place the material-carrying surface on the upper side on the return run. However, in the known devices the turnover is achieved over an extended length. This is undesirable due to the fact that the material dropped from the conveyor belt occurs over most of the length of the inversion device, thereby failing to solve the problem of material deposits. These devices suffer an additional disadvantage in that they cannot operate or be installed in a limited space. Thus, installation and operation becomes impractical.
Another problem with the known devices which invert a belt over the extended length of the return run is that the conveyor belt often drop off its guide rollers due to gravity if tension is not appropriately controlled in the belt. This may result in the conveyor belt leaving its correct path through the inversion device and becoming fouled on parts of the belt inversion device or on other equipment or structure.
Another problem associated with known types of belt inversion devices is that the distribution of tension in the conveyor belt as it is rotated through 180.degree. is altered so that there exists a higher tension in the outer (edge) portion of the conveyor belt cross-section and a lower tension in the central portion of the conveyor belt cross-section. Higher tension in the outer portion of the conveyor belt may lead to failure of the conveyor belt and of the conveyor belt splices.